In comparison with mechanical locking devices, electronic locking devices, in which the unlocking circuit is arranged to be actuated when the code of a magnetic card read by the card reader agrees with an unlocking key code set in the memory, have large merits in security and are widely used in facilities where a large number of locking devices are required such as hotels.
Such electronic locking devices installed in guest rooms of hotels require alteration of the unlocking key code of a room whenever a guest changes. If such clearing of key codes could be effected by anyone at any time, the electronic locking devices would become useless.
It is, therefore, necessary to arrange the electronic locking device so that the unlocking codes are cleared only when certain conditions are met. To be more specific, when a card (hereinafter called a clearing card) storing a certain code is inserted into the card reader of the electronic locking device. In the context of this invention, the term "clearing of key codes" is to be construed as enabling the memory under specified conditions by cancelling the flag of the memory storing key codes.
The present invention was made in view of the aforementioned circumstance, and it is an objective of the invention to make the clearing of unlocking key codes easier while retaining security of normal operation.